Biomedical Engineering Reference
In-Depth Information
1.3.7
Preoperative Assessment of Aneurysm
An aneurysm is an occlusion in the arteries caused by a blood-filled sac occurring in
the wall of the blood vessel (see later in Chap. 2). Using CHD the flow field on an
untreated and stented aneurysmal artery can be characterized. Streamline tracings
can visualize the strength and position of vortices that are present in the aneurysmal
sac. In Fig.
1.15
, a simulated model is presented to show stenting inside a diseased
artery at the aneurysm, and to demonstrate the interference with blood flow before
and after stent treatment. The reason for stent insertion inside the aneurysm is to
exclude it from the systemic blood circulation, so that the aneurysm will gradu-
ally shrink (due to reduced pressure) and eventually become insignificantly small.
While this may induce stagnation and possible thrombosis formation after stenting,
the chance of rupture is low since the aneurysm does not grow in size. Aneurysms
can form on either side of the artery wall and so simulations of different types of
diseased arterial geometries can be performed for understanding the effect of stent
treatment. Three dimensional stent models may be created based on patient-specific
aneurysm to enhance research and clinical value.
The simulated results in Fig.
1.15
demonstrate that stenting causes a reduction in
pressure, velocity, vorticity, and shear rate. The reduced pressure exerted by blood
on the aneurysmal sac will decrease the risk of rupture. However, a lower volume of
flow into the sac increases the viscosity of blood in the aneurysm (Kim et al. 2010a).
A reduced vorticity in the sac can be seen in the stented aneurysm which corresponds
Fig. 1.15
Saccular aneurysmal stent modelling and analysis. Idealistic modelling is implemented
and streamline tracing shows that the stent limits flow into the aneurysm. Different stent struts are
modelled to demonstrate the effect on local shear strain rate of blood
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